1. Field of Use
This invention relates generally to apparatus having magnetic elevator devices for moving the top or endmost object in a stack of magnetizable objects, such as steel sheets or rods, to a fixed transport position; transport means for then moving the object away from the transport position for processing; and electric control means for operating the transport means.
In particular, the invention relates to the construction of such magnetic elevator devices.
2. Description of the Prior Art
In some industrial processes, a stack of objects, such as metal sheets or rods, are provided at one location. Periodically, the uppermost or endmost object in the stack is removed from the stack and moved to another location of processing by suitable transport means. Removal and transport of the uppermost object can be facilitated if it is moved to a fixed "transport position" wherein it can be easily grasped by the transport means. In some cases, the entire stack is moved as each successive uppermost or endmost object is removed from the stack so as to ensure that the next object to be removed is automatically disposed in the transport position. In other cases, the stack itself remains stationary and means are provided to raise only the uppermost or endmost object to the transport position. The transport means may take various forms and may, for example, comprise a head member which is selectively movable vertically and horizontally between the transport position and some other location to which the objects are to be transported. The head member is provided with selectively operable lifting devices to releasably engage the object in the transport position. The lifting devices may take the form of mechanical jaws or clamps or suction cups. In cases where the objects are fabricated of magnetizable metal, such as iron or steel sheets or rods, it is possible to use electro-magnetic lifting devices to releasably engage the objects. However, there is a possibility that the lifting magnet might simultaneously attract the uppermost metal object, as well as the metal object immediately beneath or adjacent to it in the stack. Therefore, it is desirable that the magnetic object which reaches transport position be physically separated or spaced from the next adjacent object in the stack.
Apparatus and devices for magnetically separating, moving and positioning magnetizable sheet-like members arranged in a stack are known and the following U.S. patents illustrate the state of the art. Typcially, the prior art apparatus and devices are designed for very specialized purposes and some require additional mechanical lifting devices to raise the stack of members upon which the magnetic devices act.
U.S. Pat. No. 2,474,141 (Chatterton) discloses apparatus wherein a stack of magnetizable metal sheets is raised vertically by a movable platform and permanent magnetic devices located along an edge or edges of the sheets nearest the top of the stack effect magnetic separation. Non-magnetic guides associated with the magnets slidably engage the sheet edges to facilitate their upward movement.
U.S. Pat. No. 3,353,822 (Dangelmaier et al) discloses apparatus wherein sets of electro-magnetic devices arranged in alignment one above the other and are electrically switched on and off sequentially to provide a traveling magnetic field which raises magnetizable metal blanks from a stack. Metal guides engage the blank edges to provide a transport channel to facilitate upward movement.
U.S. Pat. No. 4,465,415 (Eberling et al) discloses apparatus wherein a stack of magnetizable laminations is raised vertically by a movable platform and a magnetic device in the form of a mandrel extends into a central hole of the lamination to spread them apart. The magnetic device comprises a series of electromagnets arranged in alignment one above another. The electromagnets are switchable on and off to produce desired lifting effects.